From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chen Gang Subject: Re: [PATCH v4] net: mac802154: comparision issue of type cast, finding by EXTRA_CFLAGS=-W Date: Thu, 25 Apr 2013 17:40:29 +0800 Message-ID: <5178FA0D.8060009@asianux.com> References: <5175DFBC.7040000@asianux.com> <5175F7F7.7000703@asianux.com> <51766F74.2090007@asianux.com> <20130425.041044.768895561908042668.davem@davemloft.net> <5178ECA2.6020402@asianux.com> <5178F120.5030500@acn-group.ch> Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Cc: Christophe Aeschlimann , sergei.shtylyov@cogentembedded.com, alex.bluesman.smirnov@gmail.com, dbaryshkov@gmail.com, linux-zigbee-devel@lists.sourceforge.net, netdev@vger.kernel.org To: David Miller Return-path: Received: from intranet.asianux.com ([58.214.24.6]:32745 "EHLO intranet.asianux.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756919Ab3DYJlR (ORCPT ); Thu, 25 Apr 2013 05:41:17 -0400 In-Reply-To: <5178F120.5030500@acn-group.ch> Sender: netdev-owner@vger.kernel.org List-ID: Need change ~(u8)0 to 0xff, or in mac802154_wpan_xmit(), "u8 chan" will never == MAC802154_CHAN_NONE. The related warning: net/mac802154/wpan.c:325:2: warning: comparison is always false due to limited range of data type [-Wtype-limits] The related unit test: cc -Wall -O2 -o test test.c ./test will output 'different' (after use '0xff' instead of '~(u8)0', it will output 'equal') -----------------------test code begin-------------------------------- #include typedef unsigned char u8; int main() { u8 uc = 0xff; if (uc == ~(u8)0) printf("\nequal\n"); else printf("\ndifferent\n"); return 0; } -----------------------test code end---------------------------------- Signed-off-by: Chen Gang --- net/mac802154/mac802154.h | 2 +- 1 file changed, 1 insertion(+), 1 deletion(-) diff --git a/net/mac802154/mac802154.h b/net/mac802154/mac802154.h index a4dcaf1..703c121 100644 --- a/net/mac802154/mac802154.h +++ b/net/mac802154/mac802154.h @@ -90,7 +90,7 @@ struct mac802154_sub_if_data { #define MAC802154_MAX_XMIT_ATTEMPTS 3 -#define MAC802154_CHAN_NONE (~(u8)0) /* No channel is assigned */ +#define MAC802154_CHAN_NONE 0xff /* No channel is assigned */ extern struct ieee802154_reduced_mlme_ops mac802154_mlme_reduced; extern struct ieee802154_mlme_ops mac802154_mlme_wpan; -- 1.7.11.7